1. Field of the Invention
The present invention relates to a hydraulic actuator, and more precisely, it relates to a two-stage hydraulic actuator having a cylinder device in which two pistons are inserted.
2. Description of Related Art
In a conventional hydraulic actuator, a single piston is reciprocally moved in a cylinder. A multi-stage cylinder device is also known in which a main piston and an auxiliary piston are provided in a cylinder.
To continuously carry out a series of operations, it is usually necessary to provide a cylinder device array consisting of a plurality of cylinder devices which are successively actuated, thus resulting in a complex and expensive equipment.
The primary object of the present invention is to provide a hydraulic actuator including a single cylinder device which can perform a plurality of successive operations.
Another object of the present invention is to provide a simple hydraulic actuator in which no eccentric load is produced during the operation.